This invention relates to slicing machines that are principally used for slicing, food products, particularly for slicing cheese, meat and pressed or moulded meat products.
Such a slicing machine comprises a rotating blade which either has a spiral cutting edge or has a circular cutting edge and is mounted for planetary motion, and means to feed the product towards the blade so that upon each revolution or each gyration of the blade one slice is cut from the face of the product. The means to feed the product may be a continuous conveyor but usually the slicer includes a fixed platform on which the product is placed and a feeding head which engages the rear face of the product and which urges the meat or meat product towards the blade. The feeding head is moved by a hydraulic ram or by a leadscrew driven by a stepping or variable speed electric motor.
A slicing machine is usually required to produce groups of product slices and each group is then packaged separately. This may be achieved by having the slicing machine discharge onto a constant speed conveyor and by interrupting the feed of the product towards the blade for a period of time, each time a predetermined number of slices have been cut from its face. However, more usually, the conveyor downstream from the slicing machine is a jump conveyor. In this case the jump conveyor moves at a first speed whilst the slices to form each group are being cut and then, after the number of slices required for that group have been cut, the jump conveyor moves at a second speed which is considerably faster than the first speed. The jump conveyor then returns to the first speed for the slices to form the next group. In this way the slices are cut at a uniform rate from the product but the increase in speed of the jump conveyor after each group of slices has been cut, results in a series of groups of slices being formed on the jump conveyor.
It is desirable for each group of slices to have a predetermined, required weight and various attempts and proposals have been made in the past for ways to achieve this. The principal difficulty in achieving uniformity results from the nature of the product being sliced. Food products are derived from natural products and are therefore not uniform in density. Their dimensions and hence their cross-sectional area also vary, for example pieces of meat vary with the size and shape of animal from which they have been obtained and even semi-manufactured products such as cheese and meat products formed in a mould, vary in size depending on their water content. In one way that has been proposed previously to overcome these problems slices of uniform thickness are cut from the product and the number of slices in each group is varied to achieve at least the required weight for each group of slices. This technique is rather wasteful and at times, almost a whole slice overweight is included in each group of slices. Equally, some of the other proposals vary the thickness of the slices throughout the slicing operation. Sometimes this method leads to variations in the slice thickness of the different slices in the pack which is particularly noticeable and undesirable from a commercial point of view. In any event, where fixed pack weights are obtained by varying the slice thickness, it is possible for the resulting slices to be too thick or too thin to be commercially acceptable. This is of course particularly true with meat and meat products. Equally, when providing the required pack weight by varying the number of slices there comes a point when the number of slices per pack also varies beyond the commercially desirable limit and thus, none of the existing proposals produce groups of slices that are consistently satisfactory irrespective of variations in the density and cross sectional area of the products being sliced.